In a perfect "dance world" we would have great chemistry and connection with each partner we dance with. This is not always the case, and it is not necessarily a bad thing. Each dance is unique, not one is alike, and you learn something new, whether positive or negative, from each.
Gentlemen: You should avoid teaching your partner new patterns or steps during a social dance or in a class setting. Concentrate on doing what both of you can do, and enjoy the dance. Unsolicited teaching may make your partner feel uncomfortable and takes the fun out of dancing. If you're in a class setting and find yourself struggling with your partner ask your instructor/s for help!
Ladies: You should avoid telling your partner how to lead you during a social dance. If you are in a class setting, try to avoid back leading, or anticipating the steps. Anticipating your partner's lead will cause him to get frustrated and will take the fun out of dancing. If you find yourself struggling with your partner ask your instructor/s for help!